Ultra-robust nanomembranes possessing high mechanical strength combined with excellent stiffness and toughness rarely achieved in nanocomposite materials are presented. These are fabricated by alternately depositing 1D cellulose nanocrystals and 2D graphene oxide nanosheets by using a spin assisted layer-by-layer assembly technique. Such a unique combination of 1D and 2D reinforcing nanostructures results in layered nanomaterials.

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The construction of multilength scaled hierarchical nanostructures from diverse natural components is critical in the progress toward all-natural nanocomposites with structural robustness and versatile added functionalities. Here, we report a spontaneous formation of peculiar "shish kebab" nanostructures with the periodic arrangement of silk fibroin domains along straight segments of cellulose nanofibers. We suggest that the formation of these shish kebab nanostructures is facilitated by the preferential organization of heterogeneous (β-sheets and amorphous silk) domains along the cellulose nanofiber driven by modulated axial distribution of crystalline planes, hydrogen bonding, and hydrophobic interactions as suggested by all-atom molecular dynamic simulations. Such shish kebab nanostructures enable the ultrathin membrane to possess open, transparent, mechanically robust interlocked networks with high mechanical performance with up to 30 GPa in stiffness and 260 MPa in strength. These nanoporous robust membranes allow for the extremely high water flux, up to 3.5 × 10 L h m bar combined with high rejection rate for various organic molecules, capability of capturing heavy metal ions and their further reduction into metal nanoparticles for added SERS detection capability and catalytic functionalities.

We demonstrate that stronger and more robust nacre-like laminated GO (graphene oxide)/SF (silk fibroin) nanocomposite membranes can be obtained by selectively tailoring the interfacial interactions between "bricks"-GO sheets and "mortar"-silk interlayers via controlled water vapor annealing. This facial annealing process relaxes the secondary structure of silk backbones confined between flexible GO sheets. The increased mobility leads to a significant increase in ultimate strength (by up to 41%), Young's modulus (up to 75%) and toughness (up to 45%). We suggest that local silk recrystallization is initiated in the proximity to GO surface by the hydrophobic surface regions serving as nucleation sites for β-sheet domains formation and followed by SF assembly into nanofibrils. Strong hydrophobic-hydrophobic interactions between GO layers with SF nanofibrils result in enhanced shear strength of layered packing. This work presented here not only gives a better understanding of SF and GO interfacial interactions, but also provides insight on how to enhance the mechanical properties for the nacre-mimic nanocomposites by focusing on adjusting the delicate interactions between heterogeneous "brick" and adaptive "mortar" components with water/temperature annealing routines.

Power-generating flexible thin films for facile detection of biotactile events are fabricated from patterned metal-graphene oxide biopaper. These tactile materials are mechanically robust with a consistent output of 1 V and high response rate of 20 Hz. It is demonstrated that the simple quadruple electronic skin sensitively and selectively recognizes nine spatial biotactile positions and can readily be expanded.

Novel nacre-mimic bionanocomposites, such as graphene-based laminates, are pushing the boundaries of strength and toughness as flexible engineering materials. Translating these material advances to functional flexible electronics requires methods for generating print-scalable microcircuits (conductive elements surrounded by dielectric elements) into these strong, tough, lightweight bionanocomposites. Here, we present a new paradigm for printing flexible electronics by employing facile, eco-friendly seriography to confine the reduction of graphene oxide biopapers This article is protected by copyright. All rights reserved.2 reinforced by silk interlayers to be strong and chemically-resilient. Well-defined, micro-patterned regions on the biopaper are chemically reduced, generating a 10 6 increase in conductivity (up to 10 4 S/m) in order to facilitate sensing electronic functionalities. We showcase flexible, robust graphenesilk circuits in diverse, prospective applications as resistive moisture sensors and capacitive proximity sensors. Unlike electronics generated from the printing conductive inks on substrates, seriographyguided reduction does not create mechanically weak interfaces between dissimilar materials, and do not require the judicious formulation of conductive (i.e. graphene-or Ag nanoparticle-loaded) inks. We demonstrate the unimpaired functionality of printed-in graphene-silk microcircuits after thousands of punitive folding cycles, and chemical attack by harsh solvents, hazardous conditions which usually ruin existing materials designs. This novel approach provides a low-cost, portable solution for printing micron-scale conductive features uniformly across large areas (>hundreds of cm 2 ) in layered composites for emerging applications including wearable health monitors, functional electronic skin, as well as large-scale rollable antennas and conformable displays.

This work demonstrates a facile and versatile method for generating low scattering cross-linked quantum dot (QD)-polymer composite films and patterned highly emissive structures with ultrahigh QD loading, minimal phase separation, and tunable mechanical properties. Uniform QD-polymer films are fabricated using thiol-ene chemistry, in which cross-linked polymer networks are rapidly produced in ambient conditions via fast UV polymerization in bulk to suppress QD aggregation. UV-controlled thiol-ene chemistry limits phase separation through producing highly QD loaded cross-linked composites with loadings above majority of those reported in the literature (<1%) and approaching 30%. As the QD loading is increased, the thiol and ene conversion decreases, resulting in nanocomposites with widely variable and tailorable mechanical properties as a function of UV irradiation time with an elastic modulus decreasing to 1 GPa being characteristic of reinforced elastomeric materials, in contrast to usually observed stiff and brittle materials under these loading conditions. Furthermore, we demonstrate that the thiol-ene chemistry is compatible with soft-imprint lithography, making it possible to pattern highly loaded QD films while preserving the optical properties essential for high gain and low optical loss devices. The versatility of thiol-ene chemistry to produce high-dense QD-polymer films potentially makes it an important technique for polymer-based elastomeric optical metamaterials, where efficient light propagation is critical, like peculiar waveguides, sensors, and optical gain films.

Despite noteworthy progress in the fabrication of large-area graphene sheetlike nanomaterials, the vapor-based processing still requires sophisticated equipment and a multistage handling of the material. An alternative approach to manufacturing functional graphene-based films includes the employment of graphene oxide (GO) micrometer-scale sheets as precursors. However, search for a scalable manufacturing technique for the production of high-quality GO nanoscale films with high uniformity and high electrical conductivity is still continuing. Here we show that conventional dip-coating technique can offer fabrication of high quality mono- and bilayered films made of GO sheets. The method is based on our recent discovery that encapsulating individual GO sheets in a nanometer thick molecular brush copolymer layer allows for the nearly perfect formation of the GO layers via dip coating from water. By thermal reduction the bilayers (cemented by a carbon-forming polymer linker) are converted into highly conductive and transparent reduced GO films with a high conductivity up to 10 S/cm and optical transparency on the level of 90%. The value is the highest electrical conductivity reported for thermally reduced nanoscale GO films and is close to the conductivity of indium tin oxide currently in use for transparent electronic devices, thus making these layers intriguing candidates for replacement of ITO films.